This section defines various terms used with AutoCal modules and the calibration procedures used with the VectorStar.
Insertable and Non-Insertable Devices
Insertable devices have an insertable connector pair such as a male input connector and a female output connector. These devices can be measured after a through calibration. A non-insertable device has a non-insertable pair of connectors such as female connectors on both ports or different connector types such as a DUT with both a K and V connector. Non-insertables cannot be connected directly into the measurement path without an adapter.
• Through (“Thru”)
A thru (properly called a “through”) is a connection of the two test ports. Two kinds of through connections, internal through and true through, are defined for the AutoCal calibration.
• Internal Through (“Internal Thru”)
An Internal Through is an internal path through the calibrator requiring no operator involvement in the AutoCal setup.
• True Through (“True Thru”)
A True Through is a direct cable connection between the test ports, with no intervening connectors. An internal through is not as accurate as a true through but requires more operator involvement and takes more time to accomplish. The true through can be more accurate than the internal through (if very well-matched and of very low loss) but the length and loss must be entered. The return loss of the adapters must be very good to avoid added error.
For the 36585 series of AutoCal, both the true thru and the internal thru can be processed as ‘reciprocals’. This concept is discussed in more detail in SOLT/SOLR Calibration and Reciprocal Measurements of this guide but the basic principle is that calibration will not use knowledge of the thru characteristics, but will place more weight on the accuracy of the reflection standards. In the case of the true thru, the reciprocal approach is advisable if the characteristics of the thru are not well-known and the insertion loss/mismatch are substantial. Reciprocal processing is also usually advised for the internal thru path, but defaults to using the characterization data for backwards-compatibility.
Auto-Sense
A selectable function of the AutoCal module where, if enabled, the AutoCal module decides the left/right test cable assignment. If not enabled, the operator defines the port number to left/right assignment.
Characterization File
Each calibrator module has a file containing data which characterizes each standard in the calibrator. This file also contains information (identification number, start and stop frequencies) concerning the capabilities of the calibrator. Each characterization file has the extension “.acd.” When modules are changed, the appropriate new characterization file must be installed. The files are typically stored on a Characterization Memory Device (USB memory device). Insert the Characterization Memory Device into a VectorStar USB port. This file can be installed by navigating to the INSTALL (AUTOCAL CHARACTERIZATION/CAL KIT) dialog box:
• MAIN MENU | Calibration | CALIBRATION | Cal. Kit/AutoCal Characterization | CAL KIT/AUTOCAL | Install Kit/Charac. | INSTALL (AUTOCAL CHARACTERIZATION/CAL KIT) dialog box
From the dialog box, navigate to the location of the Characterization Memory Device. Select the file, and copy it to a location within the C:\AnritsuVNA folder. In addition, each AutoCal module can be re-characterized using the VNA, although specifications are only valid if Anritsu has performed the characterization (recommended re-characterization interval is 12 months). A valid 12-term calibration must be active, which is used to characterize the standards within the module.